--  @testpoint:opengauss关键字coalesce(非保留)，作为函数名
--关键字不带引号-合理报错
drop function if exists coalesce;
create function coalesce(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
--清理环境
drop function coalesce;

--关键字带双引号-成功
drop function if exists "coalesce";
create function "coalesce"(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
--清理环境
drop function "coalesce";

--关键字带单引号-合理报错
drop function if exists 'coalesce';
create function 'coalesce'(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/

--关键字带反引号-合理报错
drop function if exists `coalesce`;
create function `coalesce`(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/